The present invention relates to scaffold fixation devices useful in articular cartilage repair and more specifically to a device for fastening an articular cartilage scaffold to underlying bone.
Tissue engineering is defined as the application of engineering disciplines to either maintain existing tissue structures or to enable new tissue growth. This engineering approach generally includes the delivery of a tissue scaffold that serves as an architectural support onto which cells may attach, proliferate, and synthesize new tissue to repair a wound or defect. Cartilage tissue scaffolds have high open-celled porosity to allow cell migration throughout the scaffold and also to allow important nutrient-bearing fluids to flow through the scaffold to maintain the health of the cells.
Articular cartilage is a tissue that covers the articulating surfaces between bones in the joints. Articular cartilage consists of two principal phases: a solid matrix and an interstitial fluid phase. The matrix, which gives cartilage its stiffness and strength, is produced and maintained by chondrocytes. Many studies have indicated that load has an important influence on matrix synthesis and on the composition of articular cartilage. Published studies have described the effect of mechanical loading on cell activity and matrix synthesis in cartilage: Hall, Urban, and Gehl, xe2x80x9cThe Effects of Hydrostatic Pressure on Matrix Synthesis in Articular Cartilagexe2x80x9d, Journal of Orthopaedic Research, Vol. 9, pp. 1-10, 1991; Freeman, Natarajan, Kimura, and Andriacchi, xe2x80x9cChondrocyte Cells Respond Mechanically to Compressive Loadsxe2x80x9d, Journal of Orthopaedic Research, Vol. 12, pp. 311-320, 1994; Tagil and Aspenberg, xe2x80x9cCartilage Induction by Controlled Mechanical Stimulation In Vivo, Journal of Orthopaedic Research, Vol. 17, pp. 200-204, 1999 and; Carver and Heath, xe2x80x9cSemi-continuous Perfusion System for Delivering Intermittent Physiological Pressure to Regenerating Cartilagexe2x80x9d, Tissue Engineering, Vol. 5, pp. 1-11, 1999.
Synthetic absorbable biocompatible polymers are well known in the art. Such polymers typically are used to manufacture medical devices which are implanted in body tissue and absorb over time. Synthetic absorbable biocompatible aliphatic polyesters include homopolymers, copolymers (random, block, segmented and graft) of monomers such as glycolic acid, glycolide, lactic acid, lactide (d, l, meso and mixtures thereof), caprolactone, trimethylene carbonate and p-dioxanone. Numerous U.S. Pat. Nos. describe these polymers, including 5,431,679; 5,403,347; 5,314,989; 5,431,679; 5,403,347; and 5,502,159. Devices made of an absorbable material have the advantage that they are absorbed by the body after healing has occurred.
U.S. Pat. No. 5,067,964 describes an articular cartilage repair piece which includes a backing layer of non-woven, felted fibrous material which is either uncoated or covered by a coating of tough, pliable material. A number of means are disclosed for fastening the repair piece to the underlying bone. U.S. Pat. Nos. 5,306,311 and 5,624,463 describe a prosthetic, resorbable articular cartilage and methods of its fabrication and insertion. U.S. Pat. No. 5,713,374 describes an attachment method to hold a biomaterial in place until healing occurs. U.S. Pat. Nos. 5,632,745 and 5,749,874 and 5,769,899 describe a bioabsorbable cartilage repair system.
High porosity is a critical design criterion in engineering of tissue scaffolds. Since a very porous tissue scaffold will have low stiffness and strength, a device is needed that will protect the scaffold from high joint loads. The same device needs to provide controlled mechanical stimulation of the cells within the scaffold to increase cell activity and matrix synthesis to produce new cartilage.
Accordingly, it would be advantageous to provide a scaffold fixation device which allows limited loading of the scaffold effective to stimulate tissue regeneration within the scaffold, while also providing protection of the scaffold from excessive loading that may damage the repairing tissue.
The present invention is directed to scaffold fixation devices comprising means for anchoring the device to bone, a load support comprising an upper surface, and means for providing deformation of the device.